Mechanical horology mainly uses friction contacts for transmitting a motion or a force from one component to another, for example in gear wheels, jumper springs, escapement components or other elements. The main defects of such friction contacts are energy losses due to friction, and the relation between the transmission of motion and the transmission of stress. For example, when two components each pivot about an axis, with the two components in contact with each other, if the angular velocity increases from the first to the second component, then the torque decreases from the first to the second component. This law is always valid, and not just on average. It follows from conservation of energy.